Some rules for assuring your friend is also a good roomie for a tour:
1. Both of you need to be honest about your personal habits.
2. Agree on a budget for extras like wine.
3. Agree not to talk all the time, down time saves a friendship
4. Each compromise on something they do not want to do.
5. Bring same number and size of suitcases to divide room space well.
6. If you are not of the same fitness, discuss how you will handle that up front.
7. Meals:agree on a meal type and budget for the splurge.
8. Separate while shopping for long periods of time.
9. Agree on safety and to which strangers you will speak.
10. Agree and stick to your plan for what happens if you need to cancel and the other person loses money. refund